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24 Cards in this Set

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General formula of amino-acid?


All known enzymes are proteins except Ribozymes.

Ribozymes are self cleaving and selfsplicing RNA molecules!

Proteins are macromolecules made from amino acids which arejoined together by a covalent bond known as a peptide bond. Afunctional protein usually have a specific 3-dimensional structure

 Proteins are the most abundant biological macromolecules occurringin all cells and all parts of cells

 Proteins are the molecular instruments through which the geneticinformation is expressed

 All the proteins are made from the same set of 20 amino acids, the body can only produce 10 out of the 20 amino acids.

 The group of 20 amino acids may be regarded as the alphabet inwhich the language of protein structure is written

Many enzymes require the presence of other compounds - cofactors - before their catalytic activity canbe exerted.

Structure of enzyme?

held together by?

structures of proteins?(folding)?

bonds in the structures?

Binding site?

Allosteric site?

They are all proteins( globular proteins). 

They are long chains of amino acid units heldtogether by peptide bonds, looped and folded into secondary and tertiary (andoften quaternary) structures by disulfide bonds, hydrophobic interactions andsa...

They are all proteins( globular proteins).

They are long chains of amino acid units heldtogether by peptide bonds, looped and folded into secondary and tertiary (andoften quaternary) structures by disulfide bonds, hydrophobic interactions andsalt bridges.

The enzyme has anactive site, that is the substrate binding site with the catalytic site and iswhere the catalyzation takes place. It has a high specificity.

There can also be anallosteric site for where the regulating molecule can attach. The enzyme isalso composed of other binding sites.

Simple enzymes?


Simple enzymes are only proteins


They have two parts:

Apoenzyme(the protein part)



Optimal temperature for the amylase action?



Starch-Iodine complex?

Boiled tube?

Unboiled tube?

How pH effects amylase?

Amylase catalyses the break down of starch into its monomers.

Denaturation is a process in which proteins or nucleic acids loose their structure (Quart,Tert,Secondary)

If amylase is exposed to temperature >70C atoms starts to vibrate so much that atoms smash into each other causing irreversible damage to the molecular structure.

Iodine angles the starch molecule into a spiral which forms the Starch-Iodine complex!

This can then be used as a marker for the presence of starch, cause if starch is present it will give a dark blue color

Boiled tube - Dark blue color cause amylase enzyme is destroyed

Unboiled tube - No color since amylase enzyme is working properly and catalyzing the breakdown of starch

Effective pH range of Amylase=6,8-7,0

Ionic charge creates the functional shape of the enzyme

When pH changes the ionic charges changes and the structure of the enzyme is altered making it stop function or work with severely reduced capacity!

Net charge of pH


Around 3?

Around 6-8?

above 11?

Zwitter ion?



Formation of peptide bonds?





Zwitter ion - No overall charge but contains parts that have + or - charge

Isoelectric Ph = Where a molecule carries no electric charge

Netcharge changes with pH and concentration

Formation of peptide bonds is followed by net loss of 1 positive and 1 negative charge per peptide bond formed.

Action of amylase?(Draw and explain)

Structures of protein?(Draw and explain)

Induced fit model?(Draw and explain)

Key lock principle?(Draw and explain)

Basic structure of proteins

Basic structure of peptide bond

(Draw and explain) ON PAPER :)

Enzymes are

Three distinctive features

Enzymes work by

biological catalysts

1) catalytic power, specificity, and regulation

2) Mainly globular proteins, but a smaller number of ribonucleic acids, calledribozymes

3) lowering the activation energy and thus acceleratingreaction rates as much as 10^21 over uncatalyzed levels

In dilute aqueous solutions under mild conditions of temperature and pH

Activity of enzymes

Rate of reaction?(see picture)

Michaelis constant

High Km

Low Km

The rate of the reaction increases as thesubstrate concentration increases until reachesVmax were reaction attains maximal velocity at that point a increase in substrate concentration does notincrease reaction rate because of saturation

Substrate concentration that causes thereaction to proceed at its half maximal velocity(1/2 Vmax) Km

High Km – low affinity to the substrate

Low Km – high affinity to the substrate

Classes of enzymes

1)One way

2)Both ways


Hydrolases - Creating 2 separate molecules and addition of H2O

Ligase - ATP involved

Lyase - Clevage of C-C, C-O, C-N, Generating double bonds


Isomerase - Geometric or structural changes

Oxireductase - (C-H forming C=O)

Transferase - Transfer of any group (NH3, CH3, PO4)








Exampes: -dehydrogenases -oxidases -peroxidases -hydroxylases -oxygenases


Exampes: -transases (such as: transaminase, transkelotase, transaldolase, transmethylase.)


Exampes: -esterases -amidases -peptidases -phosphatases -glycosidases


Exampes: -decarboxylases -aldolases -synthases -cleavage enzymes -hydrases or hydratases or dehydratases -deaminases


Exampes: -isomerases -racemases -epimerases -mutases


Exampes: -synthetases

Amyloclastic force

Amyloclasticforce that is the volume of the 0,1 % starch (stivelse) solution in millilitersthat is hydrolyzed by 1 ml saliva(spytt) at 38°C during 30 min.

1. Absolute specificity

2. Bond specificity

3. Group specificity

4. Stereospecificity

Draw reaction for each group

1) enzyme can bind only one substrate and catalize only one reaction

a) Lactase, b) Sucrase c) Maltased) Urinasee) L-glutamate dehydrogenase

2) enzyme will recognize a specific type of chemical bond in the substrate molecule but does not care about the surroundings

a. Amylase, which acts on α 1-4glycosidic bonds in starch, dextrin and glycogen. b.Lipase that hydrolyzes ester bonds in different triglycerides

3) enzyme will recognize not only a specific chemical bond but also the structure surrounding the bond

Ex. pepsin – peptide bond + Tyr, Phe, Trp

4) enzyme can recognize only a specific stereoisomer

a) L amino acid oxidase acts onlyon L amino acids.

b)α- glycosidase acts only on α- glycosidic bonds

Quantitative regulation of enzyme activity?

Qualitative regulation?

Quantitative regulation of enzyme activity?

Regulation of the expression of the gene!

Ex. LAC operon, Post-translation regulation

Qualitative regulation?

Activators and inhibitors

Inhibition and what bonds that form?

Irreversible inhibitors form covalent bonds; reversible ones use weaker modes of bonding:

Hydrogen bonds

Electrostatic interactions (salt bridges)

Lipophilic interactions

Enzyme activation

Allosteric regulation,

------Homotropic effector

------Heterotropic effector

proteolytical cleavage,

covalent modification


------protein kinases

------protein phosphatases

allosteric regulation,

An allosteric enzyme is a protein that contains one or more binding sites called allosteric sites – usually separate from its active site

Substances that bind to allosteric sites are called effectors

If the effector is a substrate, it is described as homotropic

Homotropic effector: the substrate itself serves as an effector (in most cases as positiveeffector)

Heterotropic effector : the effector is different from the substrate

example: fructose 2,6-biphosphate -> activates phosphofructokinase 1 -> increases the rate of glycolysis in response to the hormon glucagon

proteolytical cleavage,

Zymogens – inactive precursors of enzymes

Common for enzymes involved in digestion

The zymogens are activated only after they have entered the stomach or intestine

In this way the molecules they encounter along the way are protected from digestion

example: Pepsinogen --> Pepsin (In stomach)

covalent modification

Can completely turn on an inactive form of an enzyme or shut down an activeenzyme

Phosphorylation is a common example of covalent modification

Enzyme Inhibition

 Competitive (reversible, non-reversible)

 Uncompetitive

 Non-competitive

 Allosteric effect

 Covalent modification

 Proteolytic cleavage

Competitive (reversible, non-reversible)


Compete with substrate for binding to the same active site

Usually similar in structure to substrate

High concentrations of inhibitor can eliminate the binding of substrate

High concentrations of substrate can block the binding of inhibitor



IRRIVERSIBLE (Toxins, Ex. Sarin)

Sarin acts on cholinesterase by forming a covalent bond with the particular serine residue at the active site.

Fluoride is the leaving group, and the resulting phosphoester is robust and biologically inactive.

A build-up of acetylcholine in the synaptic cleft, due to the inhibition of cholinesterase, means the neurotransmitter continues to act on the muscle fibre, so that any nerve impulses are effectively continually transmitted.


 Binds reversibly to enzyme-substrate complex, but are unable to bind free enzyme

E+I--->no reaction



Binds reversibly to both free enzyme and enzyme-substrate complex

Usually binding of inhibitor is not at the active site

Usually not similar in structure to substrate

Inhibitor binds to ES-complex



Substrate also binds to EI complex



Use in medicine:

It can be used to diagnose and monitor disorders in which all types of muscle are damaged.

Which organ:

Heart and muscles

Normal level in blood:

50-330 U/L adult male

40-175 U/L adult female

Lactate dehydrogenase

1. Lactate Dehydrogenase

Lactate dehydrogenase is an enzyme found in most human cells and catalyzes the production of lactate from pyruvate

Measurement of LDH isoenzymes helps determine the location of tissue damage.

Which organ:

Heart, muscles, lungs, pancreas, liver, brain

Normal levels in blood:

140-280 U/L

Aspartate Aminotransferase (AST)

Use in medicine:

The amount of AST in the blood is directly related to the extent of the tissue damage in certain organs

Which organ:

Heart and liver

Normal levels in blood:

14-20 U/L adult males

10-36 U/L adult females

Alanine aminotransferase (ALT)

Use in medicine:

ALT is measured to see if the liver is damaged or diseased.

Which organ:


Normal levels in blood:

10-40 U/L adult male

7-35 U/L adult female

Feehlings reagent

Cu2+ Ions give the orange color

Fehlings A

Solution is blue

Fehlings B


Presence of carbohydrates in the solution gives a orange color when mixed in together in the final solution.